The present invention relates to a method and device for liquefying of a fat based mixture. The invention is particularly useful to replace or at least significantly shorten the traditional conching of fat based mixtures carried out in the chocolate making process.
In the traditional manufacture of chocolate or chocolate-like compounds, finely ground powders are dispersed in a continuous fat phase. The powders found in chocolate or chocolate-like compounds are traditionally sugar, cocoa solids and/or milk solids. These are mixed in differing proportions together with cocoa butter and/or vegetable fats, milk fats and emulsifier(s), such as lecithin. Plain chocolate is obtained by mixing sugar, cocoa butter, optionally other fats, and cocoa mass. Mills chocolate contains fat and milk non-fat solids as additional ingredients. White chocolate contains milk fat and milk non-fat solids, sugar and cocoa butter and/or vegetable fat without the addition of the cocoa mass or cocoa powder. Chocolate compounds may also be produced by using alternative fats in place of or in conjunction with natural cocoa butter. Such alternative fats belong to three main categories which are cocoa butter equivalents (CBE), cocoa butter substitutes (CBS), cocoa butter replacers (CBR). Detailed discussions of these different types of alternative fats can be found in a variety of sources, see for example, Traitler, H. et al., Journal of the American Oil Chemists Society, 62(2), 417-21 (1985).
In the traditional chocolate production method, the chocolate ingredients are normally mixed and ground in a refiner or mill to sufficiently reduce particle size of solids. Then, the paste is conched at a temperature from 50 to 110° C. for periods of time from a few hours to a few days depending on the type of product and the equipment used. The conched chocolate is then usually cooled after conching to set hard either without tempering or by tempering followed by cooling or allowing to stand for a suitable period of time.
Conching of the refined flakes is usually regarded as an essential production step for the development of the final texture of the chocolate. In the conching operation, shearing created in the conche causes the breaking up of the agglomerates, which are usually solids particles sticking together by pressure or water bonds. Then, the solids particles are coated with the fat and the fat phase finally disperses throughout the chocolate mass. Conching may additionally change the flavour and remove unwanted volatile compounds such as water or acetic acids by evaporation.
Devices for conching a chocolate refined mass have been developed for decades based on the principle of producing high shear flow on the mass by rotary means such as stripping elements or vanes revolving along an inner surface of large containers. For instance, a device for conching is known from DE 39 18 813 which consists of three axis-parallel cylindrical upwardly open chambers. These are a central main chamber with a greater diameter and two lateral subsidiary chambers. The three chambers merge into one another thereby forming the conche container. Mixing tools are disposed in each chamber on driven shafts. In general, high shearing and compression are both formed between the moving stripping tool and the static surface of the chambers. Due to the size to surface volume ratio of the known conching systems, only a small amount of chocolate mass is sheared at one time. Even while providing high shearing flow, the transition of the chocolate flake to the desired finished rheology is a time consuming process. Furthermore, the industrial conching machines occupy a considerable floor space in the factory and hence, the capital cost of these machines is very high.
Therefore, the conche is very important in the chocolate making process however it is a very inefficient mixer. With conche mixing taking up to a day to achieve the desired texture and quality, it is both an energy intensive and time consuming part of the chocolate processing.
Furthermore, the viscosity of the fat based mass is critical to produce the correct final product weight. For that, fat plays an essential role as it is the main ingredient used to coat the solid particles, plastify them and finally liquefy the mass. As fat is one of the most expensive major ingredients, any reduction of the fat content for a same level of viscosity reduction provides a significant economical advantage.
EP 0603487 A2 relates to a process for plastically extruding a fat-confectionery material comprising feeding a fat-confectionery material, usually chocolate, into an extruder barrel and applying pressure of a piston to the material in a substantially solid or semi-solid non-pourable form upstream a flow constriction of a die at a temperature at which the material is extruded isothermally. This process enables to form chocolate by extrusion. The starting material is a fat-based confectionery material in a liquid, paste or solid or semi-solid form but is already composed of solids that are already coated with the fat. Therefore, it is already chocolate product when entering into the extruder. Usually, this material is in the form of chocolate buttons. The process is a forming operation to provide a temporarily plastic end product from a solid material but is not an operation pertaining to the chocolate making process ‘per se’.
EP 0 775 446 A2 also relates to cold extrusion of chocolate where the starting material is already chocolate.
U.S. Pat. No. 4,679,498 relates to a method and apparatus to prepare in a very short time a chocolate paste from a pasty mass of solids and cocoa butter. A refined paste is subjected to a dry conching treatment in a screw conveyor, the paste being obtained being then subjected to a liquefaction treatment by incorporation of additives in proportions in proportions according to the recipe. The dry conching stage comprises a first simple kneading and a second kneading step with production of shearing and rolling which intensity increases gradually. Conching in a screw conveyor like this provides essentially shearing and rolling by the screw, then, elongational flow at the exit of the conveyor. Applying shearing and rolling is energy consuming and it also requires complex and expensive extruding equipment. Extruding equipment provides also less versatility and requires important and expensive modifications of the tooling (e.g., exchange of the screw parameters, its pitch, size and shape) if one wants to modify the final characteristics of the output product such as its viscosity.
U.S. Pat. No. 4,861,615 also relates to preparing chocolate mixtures in a twin-screw extruders.
U.S. Pat. No. 3,663,231 refers to a continuous conche used in traditional chocolate factories which provides essentially shear forces to the fat and solid mass during the dry and liquid phases.
U.S. Pat. No. 4,191,786 relates to a cooking drying method for making a powder but not a liquefied mass.
Therefore, there is a need for a method that provides a quicker, more effective and less energy consuming way for reducing the viscosity of a previously refined fat based mass.
There is also a need for significantly reducing the residence time of the product in this processing stage while providing satisfactory rheological properties to the final compound.
There is further a need for a method that requires less floor occupation and is a continuous process which makes also changeovers between products easier.
There is further a need for a method that more efficiently lowers the viscosity of a fat based bulk material while making the best use of the amount of fat available to coat the solids with fat.
There is also a need for replacing the conching or at least reduce in conching the liquefying time and/or increase the loading or throughput of material in the conche.
There is also a need for a method that enables to reduce the amount of fat for essentially the same level of viscosity.
There is also a further need to provide a lower cost manufacturing process.